The present invention relates to a read and/or write head, and is more specifically related to an improved method of parking the read and/or write head.
Heads for reading and writing information are used in data storage systems, such as disc drives. Many data storage systems are designed for both the recording and the retrieval of data, and therefore require both a write and a read head. For example, conventional disc drives are used to both record and retrieve information. Typically, one head, a read/write head, is used for both the recording and the retrieval of data. Referring to FIG. 1, multiple heads 40 (only one of which is shown) are mounted on a head stack assembly (HSA), which typically also includes a voice coil motor 16, an arm assembly 116, a preamplifier (not shown), a flexible circuit 48 and flexible circuit board 42. The flexible circuit 48 and flexible circuit board 42 connect the heads 40, and preamplifier together, and connect them to a printed circuit board 44 attached to the outside of the housing of the HSA.
FIG. 1 is an exploded view of an information storage system 10, hereinafter disc drive 10, having one or more heads 40. The disc drive 10 includes actuator arms 14 driven by a voice coil motor 16, herein after motor 16. The actuator arms 14 extend from a pivot assembly 20, located at one end of the motor 16, and over the discs 18 to position one of the heads 40 over the selected track of one of the discs 18. The motor 16 is driven thought the spindle motor, which is driven by a driver circuit 50 that responds to signals received at extension pins to provide the force necessary to rotate the actuator arms 14 about the pivot 20 to position one of the heads 40 over a desired track on one of the rotating discs 18.
Each actuator arm 14 includes a substantially triangular shape rigid arm 12 and either one or two suspensions 30 supported by the rigid arm 12. The rigid arm 12 is mounted at the pivot 20 around which the actuator arm 14 rotates. One head 40 is mounted at the opposite end of the suspension 30 from the connection to the rigid arm 12. Referring to FIG. 2, each actuator arm 14a . . . 14d can support one or two suspensions 30a . . . 30f, each supporting a head 40a . . . 40f, respectively. One suspension 30b, 30d, 30f is for writing data to and reading data from the disc 18a, 18b, 18c above the actuator arm 14b, 14c, 14d, respectively, and the other suspension 30a, 30c, 30e is for writing data to and reading data from the disc 18a, 18b, 18c below the actuator arm 14a, 14b, 14c, respectively. The top and bottom actuator arms 14a, 14d only need one suspension, designated 30a and 30f, respectively.
Referring again to FIG. 1, each of the heads 40 reads data from and writes data to selected tracks on the surface of the disc 18. In retract, the position of the heads 40 is determined by the motor 16 which is supplied by the rectified voltage on the spindle motor, rectified through the diodes on the drivers. The spindle motor responds to electrical signals from the driver circuit 50 supplied through a preamplifier (not shown).
While the disks 18 are spinning, the aerodynamics of the discs 18 and the heads 40 keep the heads 40 flying above the discs 18. When the discs 18 stop from spinning, then there is no more aerodynamics and the heads 40 tend to land on the discs 18. The heads 40 landing on the discs 18 can damage both the heads 40 and the discs 18, and can even destroy or corrupt the information on the discs 18 at the locations where the heads 40 land.
The heads 40 landing on the discs 18 is even a larger problem in laptop computers, since the computer are being moved, and occasionally dropped. This can cause the heads 40 to land on the discs 18 with a large force and damage both the heads 40 and discs 18. Additionally, with the new way discs 18 are being polished, heads 40 landing on the discs 18 even with a smaller force can damage the discs 18.
To prevent the heads 40 from landing on the discs 18, it is becoming common now for disc drives 10 to contain ramps 60 on which the heads 40 can be placed when they are parked. Referring to FIG. 3, when a retract signal notifies the disc drive 10 to stop, the heads 40a . . . 40f are driven from the location they are at to the outer diameter of the discs 18 and then up to the flat parts 62a . . . 62f of the ramps 60a . . . 60c. The ramps spread apart the suspensions 30a . . . 30f, and the head are parked on the ramps 60a . . . 60c.
One problem with parking the heads 40a . . . 40f on the ramps 60a . . . 60c is that moving the heads 40a . . . 40f to the flat part of the ramps 60a . . . 60c can require a great deal of momentum, which requires the driver circuit to generate a high current level in the motor. The back emf is used to park the heads 40a . . . 40f, and when a large current is drawn to force the heads 40a . . . 40f up the ramps the back emf can drop, causing the driver circuit 50 to fail. This leaves the heads 40a . . . 40f at the bottom of the ramps, on the outer diameter of the discs, which, as explained above, can damage both the heads and the discs, and can destroy or corrupt the information on the discs.